Method and System for Determining Hard and Preferred Rules in Global Routing of Electronic Designs

1. A computer-implemented method for determining whether to use hard rules or whether to use soft rules for a first g-cell during global routing of an integrated circuit design, comprising: performing global routing with one or more of the hard rules which comprise a first requirement for a routing demand and guide the global routing; determining, by using at least one processor, whether a first g-cell in the global routing is overcongested by at least using one or more of the soft rules, wherein the one or more of the soft rules comprise a second requirement for the routing demand and are not the hard rules; identifying or creating a marking of the first g-cell as using soft rule to improve at least a performance aspect of the integrated circuit design by using at least some of the soft rules where the first g-cell is determined not to be overcongested in the act of determining whether the first g-cell is overcongested, wherein the marking of the first g-cell indicates what rule the first g-cell is to be based at least in part upon during a routing of the integrated circuit design; and storing a result of the act of identifying the marking of the first g-cell in a tangible computer accessible medium for use in subsequent routing or displaying the result on a display apparatus.

2. The computer-implemented method of claim 1 , in which the action of determining whether the first g-cell is overcongested comprises: identifying a route in the first g-cell; identifying whether the marking of the first g-cell is using hard rule or using soft rule; determining the pitch contribution to the first g-cell based at least in part upon the marking of the first g-cell; and adjusting the pitch in the first g-cell according to the pitch contribution.

3. The computer-implemented method of claim 2 , in which the act of adjusting the pitch comprises adding or subtracting the pitch based at least in part upon the pitch contribution.

4. The computer-implemented method of claim 2 , in which the pitch contribution is a hard rule pitch where the marking of the first g-cell is using hard rule.

5. The computer-implemented method of claim 2 , in which the pitch contribution is a soft rule pitch where the marking of the first g-cell is using soft rule.

6. The computer-implemented method of claim 1 , further comprising: reevaluating congestion of the first g-cell after marking the g-cell as using soft rule.

7. The computer-implemented method of claim 6 , further comprising: marking the congestion based at least in part upon a result of the action of reevaluating the congestion; rerouting a route in a second g-cell in accordance with a result of the marking congestion action; determining whether the second g-cell is overcongested; and marking the second g-cell as using soft rule, in which the second g-cell is determined not to be overcongested.

8. The computer-implemented method of claim 1 , further comprising: determining whether a first criterion is met for the integrated circuit design.

9. The computer-implemented method of claim 8 , in which the first criterion comprises a design density control criterion.

10. The computer-implemented method of claim 8 , in which the first criterion comprises whether the route is on a critical path.

11. The computer-implemented method of claim 8 , in which the first criterion comprises whether a critical dimension is involved.

12. The computer-implemented method of claim 1 , further comprising: merging the first g-cell determined to be overcongested with a third g-cell until a second criterion is met to form a fourth g-cell, in which the third g-cell is adjacent to the first g-cell.

13. The computer-implemented method of claim 12 , in which the third g-cell is determined not to be overcongested.

14. The computer-implemented method of claim 12 , further comprising: merging the first g-cell determined to be overcongested with a fifth g-cell until a third criterion is met to form a sixth g-cell, in which the third g-cell is determined to be overcongested and the fourth g-cell is determined not to be overcongested.

15. The computer-implemented method of claim 14 , in which the third criterion comprises a second predefined cost metric for routing.

16. The computer-implemented method of claim 14 , in which the third criterion comprises a first minimum threshold number of components within the fifth g-cell to be considered during global routing.

17. The computer-implemented method of claim 14 , in which the third criterion comprises a second maximum threshold number of g-cells in the integrated circuit design.

18. The computer-implemented method of claim 12 , further comprising: determining whether the fourth g-cell inherits the marking from the first g-cell; identifying a marking of design rule for the fourth g-cell; performing the global routing in the fourth g-cell; evaluating congestion of the fourth g-cell based at least in part on a second corresponding soft rule; and determining whether the fourth g-cell is overcongested based at least in part upon a result of the action of evaluating the congestion of the fourth g-cell based at least in part on the second corresponding soft rule.

19. The computer-implemented method of claim 18 , in which the marking for the fourth g-cell is using hard rule, where the fourth g-cell does not inherit marking of design rule from the first g-cell.

20. The computer-implemented method of claim 18 , in which the marking of design rule for the fourth g-cell is identical to the marking of the first g-cell, where the fourth g-cell inherits marking of design rule from the first g-cell.

21. The computer-implemented method of claim 18 , further comprising: undoing the action of merging the first g-cell with a third g-cell, in which the fourth g-cell is determined to be overcongested.

22. The computer-implemented method of claim 18 , further comprising: marking the fourth g-cell as using hard rule, in which the fourth g-cell is determined to be overcongested under the second corresponding soft rule.

23. The computer-implemented method of claim 18 , further comprising: marking the fourth g-cell as using soft rule, in which the fourth g-cell is determined not to be overcongested under the second corresponding soft rule.

24. The computer-implemented method of claim 12 , in which the second criterion comprises a first predefined cost metric for routing.

25. The computer-implemented method of claim 12 , in which the second criterion comprises a first maximum threshold number of components within the fourth g-cell to be considered during global routing.

26. The computer-implemented method of claim 12 , in which the second criterion comprises a second maximum threshold number of g-cells in the integrated circuit design.

27. The computer-implemented method of claim 1 , in which the action of determining congestion comprises: determining a routing demand of the first g-cell; determining a routing capacity of the first g-cell; and identifying the first g-cell as overcongested based at least in part upon the routing demand and the routing capacity.

28. The computer-implemented method of claim 1 , further comprising: uncoarsening the first g-cell determined not to be overcongested until a fourth criterion is met to form a set of g-cells comprising a seventh g-cell.

29. The computer-implemented method of claim 28 , in which the seventh g-cell is identical to the first g-cell.

30. The computer-implemented method of claim 28 , further comprising: determining whether the seventh g-cell inherits a marking of design rule from the first g-cell; identifying a marking of design rule for the seventh g-cell; performing global routing in at least the seventh g-cell; evaluating congestion of the seventh g-cell under a third corresponding soft rule; and determining, under the third corresponding soft rule, whether the seventh g-cell is overcongested based at least in part upon the congestion of the seventh g-cell.

31. The computer-implemented method of claim 30 , in which the marking for the seventh g-cell is using hard rule, where the seventh g-cell does not inherit marking of design rule from the first g-cell.

32. The computer-implemented method of claim 30 , in which the marking for the fourth g-cell is identical to the marking for the first g-cell, where the seventh g-cell inherits marking of design rule from the first g-cell.

33. The computer-implemented method of claim 30 , further comprising: undoing the action of uncoarsening the first g-cell, in which the seventh g-cell is determined to be overcongested.

34. The computer-implemented method of claim 30 , further comprising: marking the seventh g-cell as using hard rule, in which the seventh g-cell is determined to be overcongested under the third corresponding soft rule.

35. The computer-implemented method of claim 30 , further comprising: marking the fourth g-cell as using soft rule, in which the seventh g-cell is determined not to be overcongested under the third corresponding soft rule.

36. The computer-implemented method of claim 28 , in which the fourth criterion comprises a predefined uncoarsening scheme.

37. The computer-implemented method of claim 28 , in which the fourth criterion comprises a minimum threshold number of g-cells in the set of g-cells.

38. The computer-implemented method of claim 28 , in which the fourth criterion comprises a result of congestion evaluation of the set of g-cells.

39. A system for determining whether to use the hard rules or whether to use the preferred rules for a first g-cell during global routing of an integrated circuit design, comprising: at least one processor configured for: performing global routing with one or more hard rules which comprise a first requirement for a routing demand and guide the global routing; determining whether a first g-cell in the global routing is overcongested by at least using one or more of the soft rules, wherein the one or more of the soft rules comprise a second requirement for the routing demand and are not the hard rules; and identifying or creating a marking of the first g-cell as using soft rule to improve at least a performance aspect of the integrated circuit design by using at least some of the soft rules where the first g-cell is determined not to be overcongested in the act of determining whether the first g-cell is overcongested, wherein the marking of the first g-cell indicates what rule the first g-cell is to be based at least in part upon during a routing of the integrated circuit design; and a non-transitory tangible computer readable medium or a storage device configured for storing a result produced by the means for identifying the marking of the first g-cell for use in subsequent routing or a display apparatus configured for displaying, the result.

40. The system of claim 39 , in which the at least one processor programmed for determining whether the first g-cell is overcongested is further programmed for: identifying a route in the first g-cell; identifying whether the marking of the first g-cell is using hard rule or using soft rule; determining a pitch contribution to the first g-cell based at least in part upon the marking of the first g-cell; and adjusting a pitch in the first g-cell according to the pitch contribution.

41. The system of claim 39 , in which the at least one processor is further programmed for: reevaluating congestion of the first g-cell after marking the g-cell as using soft rule; marking congestion based at least in part upon a result of the reevaluating action; rerouting a route in a second g-cell in accordance with a result of the marking congestion action; determining whether the second g-cell is overcongested; and marking the second g-cell as using soft rule, in which the second g-cell is determined not to be overcongested.

42. The system of claim 39 , the at least one processor being further programmed for: merging the first g-cell determined to be overcongested with a third g-cell until a second criterion is met to form a fourth g-cell, in which the third g-cell is adjacent to the first g-cell; determining whether the fourth g-cell inherits marking of design rule from the first g-cell; identifying a marking of design rule for the fourth g-cell; performing global routing in the fourth g-cell; evaluating congestion of the fourth g-cell based at least in part on a second corresponding soft rule; and determining whether the fourth g-cell is overcongested based at least in part upon a result of the action of evaluating congestion of the fourth g-cell based at least in part on the second corresponding soft rule.

43. The system of claim 39 , in which the at least one processor is further programmed for: determining a routing demand of the first g-cell; determining a routing capacity of the first g-cell; and identifying the first g-cell as overcongested based at least in part upon the routing demand and the routing capacity.

44. The system of claim 39 , the at least one processor is further programmed for: uncoarsening the first g-cell determined not to be overcongested until a fourth criterion is met to form a set of g-cells comprising a seventh g-cell; and uncoarsening the first g-cell determined not to be overcongested until a fourth criterion is met to form a set of g-cells comprising a seventh g-cell.

45. The system of claim 44 , the at least one processor is further programmed for: determining whether the seventh g-cell inherits a marking of design rule from the first g-cell; identifying a marking of design rule for the seventh g-cell; performing global routing in at least the seventh g-cell; evaluating congestion of the seventh g-cell under a third corresponding soft rule; and determining, under the third corresponding soft rule, whether the seventh g-cell is overcongested based at least in part upon the congestion of the seventh g-cell.

46. A computer program product comprising a non-transitory computer-usable storage medium having executable code which, when executed by a processor, causes the processor to execute a process for determining whether to use the hard rules or whether to use the preferred rules for a first g-cell during global routing of an integrated circuit design, the process comprising: performing global routing with one or more hard rules which comprise a first requirement for a routing demand and guide the global routing; determining, by using at least one processor, whether a first g-cell in the global routing is overcongested by at least using one or more of the soft rules, wherein the one or more of the soft rules comprise a second requirement for the routing demand and are not the hard rules; identifying or creating a marking of the first g-cell as using soft rule to improve at least a performance aspect of the integrated circuit design by using at least some of the soft rules where the first g-cell is determined not to be overcongested in the ac of determining whether the first g-cell is overcongested, wherein the marking of the first g-cell indicates what rule the first g-cell is to be based at least in part upon during a routing of the integrated circuit; and storing a result of the act of identifying the marking of the first g-cell in a non-transitory tangible computer accessible storage medium for use in subsequent routing or displaying the result on a display apparatus.

47. The computer program product of claim 46 , in which act of determining whether the first g-cell is overcongested further comprises: identifying a route in the first g-cell; identifying whether the marking of the first g-cell is using hard rule or using soft rule; determining a pitch contribution to the first g-cell based at least in part upon the marking of the first g-cell; and adjusting a pitch in the first g-cell according to the pitch contribution.

48. The computer program product of claim 46 , the process further comprising: reevaluating congestion of the first g-cell after marking the g-cell as using soft rule; marking congestion based at least in part upon a result of the reevaluating action; rerouting a route in a second g-cell in accordance with a result of the marking congestion action; determining whether the second g-cell is overcongested; and marking the second g-cell as using soft rule, in which the second g-cell is determined not to be overcongested.

49. The computer program product of claim 46 , further comprising: merging the first g-cell determined to be overcongested with a third g-cell until a second criterion is met to form a fourth g-cell, in which the third g-cell is adjacent to the first g-cell; determining whether the fourth g-cell inherits marking of design rule from the first g-cell; identifying a marking of design rule for the fourth g-cell; performing global routing in the fourth g-cell; evaluating congestion of the fourth g-cell based at least in part on a second corresponding soft rule; and determining whether the fourth g-cell is overcongested based at least in part upon a result of the action of evaluating congestion of the fourth g-cell based at least in part on the second corresponding soft rule.

50. The computer program product of claim 46 , further comprising: determining a routing demand of the first g-cell; determining a routing capacity of the first g-cell; and identifying the first g-cell as overcongested based at least in part upon the routing demand and the routing capacity.

51. The computer program product of claim 46 , further comprising: uncoarsening the first g-cell determined not to be overcongested until a fourth criterion is met to form a set of g-cells comprising a seventh g-cell; and uncoarsening the first g-cell determined not to be overcongested until a fourth criterion is met to form a set of g-cells comprising a seventh g-cell.

52. The computer program product of claim 51 , further comprising: determining whether the seventh g-cell inherits a marking of design rule from the first g-cell; identifying a marking of design rule for the seventh g-cell; performing global routing in at least the seventh g-cell; evaluating congestion of the seventh g-cell under a third corresponding soft rule; and determining, under the third corresponding soft rule, whether the seventh g-cell is overcongested based at least in part upon the congestion of the seventh g-cell.

53. The computer-implemented method of claim 1 , further comprising: performing detailed routing based at least in part upon the marking of the first g-cell as using soft rule rather than involving a rip-up and reroute process for a portion of the integrated circuit design, wherein at least one of the one or more of the soft rules increases the routing demand in a portion of the integrated circuit design comprising the first g-cell.